Variable capacity swash plate type refrigerant compressor having a double fulcrum hinge mechanism

ABSTRACT

A variable capacity single headed piston swash plate type refrigerant compressor is provided with a double fulcrum hinge mechanism having a pair of hinges for providing a pivotal connection between a rotary support element of a drive shaft and a swash plate assembly, causing reciprocation of a plurality of single headed pistons in cylinder bores for compressing a refrigerant gas. The pair of hinges of the double fulcrum hinge mechanism cooperate to absorb reaction forces of the compression and suction of the refrigerant gas acting from the pistons on the swash plate assembly to thereby prevent application of a local load to a sleeve element on which the swash plate assembly is turnably mounted.

TECHNICAL FIELD

The present invention relates to a variable capacity swash plate typerefrigerant compressor mainly used for an airconditioner for a car. Moreparticularly, it relates to a variable capacity single headed pistonswash plate type compressor provided with a double fulcrum hingemechanism able to pivotally support a variable inclination swash plateassembly while preventing an application of an excessive load to asleeve element on which the variable inclination swash plate assembly isturnably mounted.

BACKGROUND ART

Japanese Unexamined (Kokai) Utility Model Publication No. 62-183082,published on Nov. 20, 1987 by the Japanese Patent Office, discloses avariable capacity swash plate type compressor having single headedpistons therein. The variable capacity swash plate type compressor ofJapanese Unexamined Utility Model Publication '082 includes a cylinderblock having a crank chamber formed therein for housing an inclinationchangeable wobble plate assembly, and a plurality of cylinder bores inwhich a plurality of single headed pistons are reciprocally fitted, tosuck and compress a refrigerant gas and to discharge the compressedrefrigerant gas. The wobble plate assembly includes a rotary driveelement rotatable with the drive shaft and a swash plate non-rotatablysupported on the rotary drive element, and is driven by a rotatablysupported axial drive shaft to which a lug member is fixedly attached tobe projected radially and rotated together with the drive shaft withinthe crank chamber. The lug member is operatively connected to the rotarydrive element of the wobble plate assembly via a hinge mechanism, and asleeve element slidably mounted on the drive shaft is also operativelyconnected to the rotary drive element of the wobble plate assembly.Namely, the rotary drive element is able to be rotated together with thedrive shaft and to change an angle of inclination thereof from an erectposition corresponding to a small compression capacity position to afully inclined position corresponding to a large compression capacityposition. The hinge mechanism includes an elongated guide hole boredthrough the lug member, and a hinge pin having one end movably fitted inthe elongated guide hole of the lug member and the other end fixed to aswing plate member extended from the rotary drive plate. The sleeveelement is arranged to be axially slid, and provided with a lateral pinradially projected therefrom to form trunnion pins about which therotary drive plate is pivotally mounted. The swash plate of the wobbleplate assembly is operatively connected to the plurality of pistons viarespective piston rods having ball-and-socket joints on both ends, andthus, when the drive shaft is rotated, the rotation of the drive shaftand the rotary drive element is converted into a reciprocation of therespective pistons in the cylinder bores. The cylinder block has acommunication passageway formed therein and extended between the crankchamber and a suction chamber, for receiving therein the refrigerant gasbefore compression and an extent of the communication between theabovementioned two chambers is controlled by a capacity control valve.

With the above-mentioned compressor, when the respective pistons arereciprocated in response to the rotation of the drive shaft, therefrigerant gas before compression is pumped from the suction chamberinto the cylinder bores, to be compressed by the pistons during thesuction and compression strokes of the pistons, and the compressed gasis discharged from the cylinder bores toward a discharge chamber for therefrigerant gas after compression. During the operation of thecompressor, a force consisting of first and second forces acts on thewobble plate assembly from the pistons, as a reaction of the compressionand suction of the refrigerant gas by the pistons, and the wobble plateassembly is physically supported by the hinge mechanism at a fulcrumposition thereof at which the hinge pin is in contact with the guidewall of the elongated guide hole of the lug member.

The construction of the above-mentioned hinge mechanism including theprojected lug member radially projected from the drive shaft and thehinge pin in engagement with the elongated hole of the lug memberresults in an arrangement such that the fulcrum position of the hingemechanism is moved around the axis of the drive shaft so as toconstantly correspond to a given position of the swash plate at whichthe swash plate is connected to one of the pistons moved in the cylinderbore to the top dead center "T" thereof from the bottom dead center "B,"thereof, as diagrammatically illustrated in FIG. 6 of the accompanyingdrawings, during the rotation of the rotary drive element of the wobbleplate assembly. Nevertheless, when each of the pistons approaches thetop dead center "T" thereof during the reciprocation thereof, thedischarge of the compressed refrigerant gas from the cylinder boretoward the discharge chamber is completed, and as soon as the movementof the piston is reversed at the top dead center "T", the suction of therefrigerant gas before compression is subsequently carried out for atime between "T" and "B₂ " of FIG. 6. Therefore, when each piston ismoved between the bottom dead position "B₁ " and the top dead center"T", the piston applies the first force to the swash plate, as areaction of the compression of the refrigerant gas, and when the pistonis moved between the top dead center "T" and the bottom dead center "B₂" the piston applies the second force to the swash plate, as a reactionof the suction of the refrigerant gas. Accordingly, the total force ofthe first and second forces acting from each piston on the wobble plateassembly is concentrated at a position of the assembly shifted from thefulcrum position "P" of the hinge mechanism in a direction of therotation of the rotary drive plate of the wobble plate assembly, and anamount of the shift depends on the number of rotations of the driveshaft, and the compression ratio of the refrigerant gas or the angle ofinclination of the wobble plate assembly. Therefore, the wobble plateassembly supported by the fulcrum position of the hinge mechanism mustbe subjected to a bending moment due to the shifting of the position atwhich the total force of the first and second reaction forces acts onthe wobble plate assembly from the fulcrum position of the hingemechanism. This bending moment acting on the wobble plate assembly isabsorbed by the sleeve element to thereby apply an excessive local forceto the sleeve element, and as a result, an abnormal noise is generatedwhen the sleeve is slid on the drive shaft and the physical durabilityof the sleeve element is reduced.

DISCLOSURE OF THE INVENTION

Therefore, an object of the present invention is to obviate the problemsencountered by the abovementioned variable capacity-single headed pistonswash plate type refrigerant compressor according to the prior art.

Another object of the present invention is to provide a variablecapacity single headed piston swash plate type compressor provided witha novel double fulcrum type hinge mechanism for pivotally supporting avariable inclination rotary swash plate assembly in a manner such that aload applied to a slidable sleeve element on which the swash plate isturnably mounted is reduced when a force consisting of reaction forcesof compression and suction of a refrigerant gas is imposed on the swashplate by pistons reciprocating in cylinder bores.

In accordance with the present invention, there is provided a variablecapacity single headed piston swash plate type compressor including:

an axially extended cylinder block having front and rear ends thereofand a plurality of axial cylinder bores formed therein;

a front housing sealingly connected to the front end of the cylinderblock and defining a closed crank chamber therein extending in front ofends of the cylinder bores;

a rear housing connected to the rear end of the cylinder block anddefining therein a suction chamber for a refrigerant gas beforecompression and a discharge chamber for the refrigerant gas aftercompression;

a drive shaft rotatably held by the cylinder block and the front housingand having an axis thereof axially extended through the crank chamber;

a rotary support element mounted on the drive shaft to be rotatedtherewith in the crank chamber;

a variable inclination rotary swash plate assembly pivotally held by ahinge means and slidably mounted around the drive shaft via a slidablesleeve element and capable of turning about an axis perpendicular to theaxis of the drive shaft to thereby vary an angle of inclination thereof;

a plurality of reciprocatory single headed pistons fitted in thecylinder bores of the cylinder block and engaged with the swash plateassembly via a motion conversion means for converting a rotation of theswash plate assembly into a reciprocation of the single headed pistonsin the cylinder bores; and

a control valve means for adjusting a fluid pressure in the crankchamber to thereby control a capacity of the compressor, wherein thehinge means is provided with a pair of hinges to provide two fulcrumpositions about which the swash plate assembly is pivotally hinged, thetwo fulcrum positions being arranged to be spaced apart from one anotherwith respect to a center position which lies in a plane including theaxis of the drive shaft and passing through a predetermined position ofthe swash plate assembly at which the swash plate assembly is engagedwith one of the plurality of pistons brought to a top dead centerthereof.

Since the two fulcrum positions of the hinge mean are symmetricallyarranged on opposite sides of the plane passing through thepredetermined position of the swash plate assembly at which the swashplate assembly is engaged with one of the plurality of pistons moved toa top dead center thereof, one of the two fulcrum positionsappropriately absorbs a reaction force of the compression of therefrigerant gas acting from the pistons on the swash plate assemblywhile the other of the two fulcrum positions appropriately absorbs areaction force of the suction of the refrigerant gas acting from thepistons on the swash plate assembly. Namely, the hinge means having thetwo fulcrum positions always can absorb a total force of the reactionforces of the compression and suction of the refrigerant gas, so thatthe swash plate assembly is not subjected to an unfavorable bendingmoment, and thus a local load is not applied to the sleeve element.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be made more apparent from the ensuing description of theembodiments thereof with reference to the accompanying drawings wherein:

FIG. 1 is a cross-sectional view of a variable capacity single headedpiston swash plate type compressor provided with a double fulcrum hingemeans according to a first embodiment of the present invention;

FIG. 2 is a partial cross-sectional view taken along the line II--II ofFIG. 1;

FIG. 3 is a diagrammatical view indicating a relationship between thetime and position of a piston with respect to the compressor accordingto the present invention;

FIG. 4 is a cross-sectional view of a variable capacity single headedpiston swash plate type compressor provided with a double fulcrum hingemeans according to a second embodiment of the present invention;

FIG. 5 is a partial cross-sectional view taken along the line V--V ofFIG. 4; and

FIG. 6 is a diagrammatical view indicating a relationship between thetime and position of a piston with respect to the compressor accordingto the prior art.

BEST MODE OF CARRYING OUT THE INVENTION

The description of a variable capacity swash plate type refrigerantcompressor of a first embodiment of the present invention will beprovided below with reference to FIGS. 1 through 3.

As best illustrated in FIG. 1, the variable capacity swash plate typerefrigerant compressor of the first embodiment has a cylinder block 1having a plurality of cylinder bores 1a, and front and rear ends of thecylinder block 1 are sealingly closed by front and rear housings 2 and3. The cylinder block 1 and the front housing 2 defines an air-tightsealed cylindrical crank chamber 2a therebetween to house a swash plateassembly including a cylindrical rotary drive element 11 and a swashplate 15 therein. A valve plate 12 is intervened between the rear end ofthe cylinder block 1 and the rear housing 3 having formed therein asuction chamber 3a and a discharge chamber 3b which can be communicatedwith the cylinder bores 1a of the cylinder block 1 via suction anddischarge valve mechanisms, respectively. An axial drive shaft 4 iscentrally arranged to extend through the front housing 2 and thecylinder block 1, and rotatably supported by bearings mounted in thefront housing 2 and the cylinder block 1. A front end of the drive shaft4 is outwardly extended from the front housing 2 to be connectable to adrive source such as a car engine, and a rear end of the drive shaft 4is rotatably supported by the bearing in the cylinder block 1.

A rotary support 5 is fixedly mounted on the drive shaft 4 in the crankchamber 2a to be rotatable with the drive shaft 4. The rotary support 5is axially supported by a thrust bearing seated on an inner end of thefront housing 2, and has rearwardly extended two support arms 6 forsupporting a cylindrical rotary drive element 11 of the swash plateassembly via a hinge means having a pair of hinges designated by "K", asshown in FIG. 2.

As will be understood from FIG. 2, the two hinges K provide a pivotalconnection between the rotary support 5 and the rotary drive element 11,and are arranged in a manner such that the hinges K are equidistantlyspaced from one another with respect to a center position lying in aplane which extends to include therein an axis of the drive shaft 4 andwhich passes through a predetermined position of the swash plate 15 atwhich the swash plate 15 is engaged with one of a plurality of pistons19 brought to a top dead center "T" thereof. More specifically, thehinge means having the two hinges K is arranged between the two supportarms 6 of the rotary support 5 and a front end of the cylindrical driveelement 11.

Referring to both FIG. 1 and FIG. 2, both support arms 6 of the rotarysupport 5 are axially rearwardly extended, and arranged to besymmetrical with respect to the above-mentioned plane including thereinthe axis of the drive shaft 4 and passing through the predeterminedposition of the swash plate 15 at which the swash plate 15 is engagedwith the piston brought to the top dead center T thereof. Each of thesupport arms 6 has a through-bore 6a in which a race member 8 is fixedlyseated to turnably receive a ball element 9. The ball element 9 hasformed therein a through-hole 9a operative as a guide hole permitting anaxial slide of a guide pin 10 therein. The guide pins 10 of the twosupport arms 6 of the pair of hinges K are arranged to be in parallelwith one another.

The rotary drive element 11 of the swash plate assembly has formedtherein two through-bores 11a, in which the guide pins 10 are fixedlypress-fitted. Namely, the two hinges K of the hinge means define a pairof hinge positions P₁ and P₂ arranged symmetrically with respect to theplane passing through the predetermined position of the swash plate 15at which the swash plate 15 is engaged with the piston 19 brought to thetop dead center thereof.

As illustrated in FIG. 3, in accordance with the above-describedsymmetrical arrangement of the hinge positions P₁ and P₂ of the pair ofhinges K of the hinge means, the hinge position P₁ is arranged topresent a pivotal connection between one of the support arms 6 of therotary support 5 and a portion of the rotary drive element 11 of theswash plate assembly, which portion acts to move each single headedpiston 19 to an intermediate position of the entire compression strokethereof, and the hinge position P₂ is arranged to present a pivotalconnection between the other of the support arms 6 of the rotary support5 and a different portion of the rotary drive element 11 of the swashplate assembly, which portion acts to move each piston 19 to anintermediate position of the entire suction stroke thereof.

The swash plate 15 mounted on the rotary drive element 11 is tightlyfixed by a ring 16 threadedly engaged with a hub portion of the driveelement 11. The swash plate 15 is provided with support rails 15c onboth faces thereof extended annularly around the axis of the drive shaft4, and these support rails 15c are slidably engaged with respectiveguide grooves of inner shoes 17 having a spherical back face,respectively, and thus the inner shoes 17 are prevented from beingshifted in a radial direction of the swash plate 15. The inner shoes 17are engaged with semi-cylindrical outer shoes 18 in such a manner thatthe spherical back faces of the inner shoes 17 are in sliding contactwith cylindrical inner faces of the outer shoes 18 outer faces of whichare also shaped in a cylindrical face, respectively, These cylindricalouter faces of the outer shoes 18 are in sliding contact withcylindrical walls of a cutout 19a of each piston 19. The cutout 19a isrecessed in a direction perpendicular to the axis of the piston 19 andprovided for permitting a passage of the swash plate 15 therethroughduring the rotation of the swash plate 15. Namely, the inner and outershoes 17 and 18 are provided as a motion conversion means for convertingthe rotation of the inclined swash plate 15 into a reciprocation of eachof the pistons 19 in the cylinder bore 1a.

The rotary drive element 11 is mounted on a sleeve 13 slidably mountedon the drive shaft 4. The sleeve element 13 is axially slidable on thedrive shaft 4 under spring forces of springs 20a and 20b arranged onopposite sides of the sleeve element 13, and an outer spherical face ofthe sleeve element 13 is in turnable contact with a spherical inner faceof the rotary drive element 11, Thus, the swash plate 15 of the swashplate assembly can be rotated with the drive shaft 4 via the rotarysupport 5 and the rotary drive element 11, and turned to change an angleof inclination thereof via the two hinges K of the hinge means and thesleeve element 13.

Control valves 21 are provided in the rear housing 3 for adjusting afluid pressure level within the crank chamber 2a as shown in FIG. 1.

When the drive shaft 4 is rotated, the swash plate 15 of the swash plateassembly having an angle of inclination is rotated also, and thus therotation of the inclined swash plate 15 is converted into areciprocation of the pistons 19 in the cylinder bores 1a via the motionconversion means having the abovementioned inner and outer shoes 17 and18. Therefore, a refrigerant gas is pumped from the suction chamber 3aof the rear housing 3 into the respective cylinder bores 1a in which therefrigerant gas is compressed by the reciprocating pistons 19. Thecompressed refrigerant gas is discharged from the cylinder bores 1atoward the discharge chamber 3b of the rear housing 3. The capacity ofthe compressed refrigerant gas discharged toward the discharge chamber3b is controlled by adjusting the fluid pressure level within the crankchamber 2a by the control valves 21. Namely, when the fluid pressurelevel within the crank chamber 2a is lowered by the operation of thecontrol valves 21 with respect to a suction pressure level, a backpressure acting on the respective pistons 19 is reduced, andaccordingly, the angle of inclination of the swash plate 15 isincreased. Namely, in the respective hinges K of the hinge means, theball elements 9 of the respective hinges K are turned in the racemembers 8 while permitting the respective guide pins 10 to slide withrespect to the ball elements 9, i.e., the guide pins 10 axially slidethrough the through-holes 9a of the ball elements 9. Therefore, therotary drive element 11 of the swash plate assembly is turned about thesleeve 13 sliding axially in the forward direction against the springforce of the lefthand spring 20b. Accordingly, the angle of inclinationof the swash plate 15 with respect to a plane perpendicular to the axisof the drive shaft 4 is increased, and thus the inner shoes 17 of themotion conversion means are slidingly turned in the outer shoes 18 whichslide radially with respect to the axis of the respective piston 19. Asa result, the stroke of the respective pistons 19 is extended to therebyincrease the compression capacity of the compressor. When the swashplate 15 reaches the largest inclination position, the largest capacityoperation of the compressor is performed.

On the contrary, when the control valves 21 closes a fluid connectionbetween the crank chamber 2a and the suction chamber 3a, to therebyprevent an extraction of the fluid pressure from the crank chamber 2a,the fluid pressure level within the crank chamber 2a is raised by ablow-by gas leaking from the cylinder bores 1a into the crank chamber2a, and thus a back pressure acting on the respective pistons 19 becomeslarge enough to decrease an angle of inclination of the swash plate 15.Namely, in the respective hinges K of the hinge means, the ball elements9 are slidingly turned in the race members 8 to thereby turn the rotarydrive element 11 about the sleeve element 13 in a counterclockwisedirection in FIG. 1 via the parallel-arranged guide pins 10. Also, thesleeve element 13 is slid in the rearward direction against the springforce of the righthand spring 20a. Therefore, the guide pins 10 areslidingly moved out of the ball elements 9 to thereby permit the swashplate 15 to turn toward a small inclination angle position thereof, andthus the turning of the inner shoes 17 and the sliding of the outershoes 18 of the motion conversion means occur to thereby shorten thereciprocating stroke of the respective pistons 19. Accordingly, thecompression capacity of the compressor is decreased. When the swashplate 15 reaches the smallest inclination angle position thereof, i.e.,an erect position thereof, the smallest capacity operation of thecompressor is performed.

During the above-mentioned compressing operation of the compressor, oneof the hinges K of the hinge means having the hinge position P₁contributes to the absorbing of the entire reaction forces acting fromthe respective pistons 19 in the compression stroke thereof on the swashplate 15 via the motion conversion means in response to the compressionof the refrigerant gas by these pistons 19 in the compression strokethereof, and the other hinge K of the hinge means having the hingeposition P₂ contributes to the absorbing of the entire reaction forcesacting from the respective pistons 19 in the suction stroke thereof onthe swash plate 15 via the motion conversion means in response to thesuction of the refrigerant gas by these pistons 19 in the suction strokethereof. Further, since the two hinges K of the hinge means cancooperate to provide a constant contribution to the absorbing of thereaction forces of the compression and suction of the refrigerant gasduring a complete rotation of the swash plate assembly, the swash plate15 of the swash plate assembly is not subjected to an unfavorablebending moment, and thus the sleeve element 13 on which the assembly isturnably mounted does not suffer from an application of a local load bythe swash plate assembly. Namely, the sleeve element 13 is able topermit a smooth turn of the swash plate assembly, which is constantlymaintained in a spherical contact with the outer spherical face of thesleeve element 13.

With the described construction of the compressor of FIGS. 1 through 3,the cooperation of the double fulcrum hinge means having the pair ofhinges K arranged to be equidistantly spaced from the plane includingthe axis of the drive shaft and passing the predetermined position ofthe swash plate 15 at which the swash plate 15 is engaged with one ofthe single headed pistons 19 brought to the top dead center "T" thereof,and the sleeve element 13 having the spherical outer face in a sphericalcontact with the swash plate assembly enables an elimination of theconventional sleeve pins arranged between the conventional sleeveelement and the wobble plate assembly to absorb a bending moment actingon the wobble plate assembly. Thus, the sleeve element 13 employed forthe compressor of the present invention can avoid a local abrasionthereof, and exhibit a long operation life without causing noise duringthe operation of the compressor.

Referring to FIG. 4 illustrating a variable capacity single headedpiston swash plate compressor according to a second embodiment of thepresent invention, a cylinder block 31 having a plurality of cylinderbores 31a, and front and rear ends of the cylinder block 31 aresealingly closed by front and rear housings 32 and 33. The cylinderblock 31 and the front housing 32 defines an air-tight sealedcylindrical crank chamber 32a therebetween to house a swash plateassembly including a swash plate 37 therein. A valve plate 40 isintervened between the rear end of the cylinder block 31 and the rearhousing 33 having formed therein a suction chamber 33a and a dischargechamber 33b which can be communicated with the cylinder bores 31a of thecylinder block 31 via suction and discharge valve mechanisms,respectively. An axial drive shaft 34 is centrally arranged to extendthrough the front housing 32 and the cylinder block 31, and rotatablysupported by bearings mounted in the front housing 32 and the cylinderblock 31. A front end of the drive shaft 34 is outwardly extended fromthe front housing 32 to be connectable to a drive source such as a carengine, and a rear end of the drive shaft 34 is rotatably supported bythe bearing in the cylinder block 31.

A rotary support 35 is fixedly mounted on the drive shaft 4 in the crankchamber 32a to be rotatable with the drive shaft 34. The rotary support35 is axially supported by a thrust bearing seated on an inner end ofthe front housing 32, and has two rearwardly extended support arms 35afor pivotally supporting the swash plate assembly via a hinge meanshaving a pair of hinges designated by "M", as shown in FIG. 5.

As will be understood from FIGS. 4 and 5, the two hinges M provide apivotal connection between the two support arms 35a of the rotarysupport 35 and a pair of swing plates 37a fixed to the swash plateassembly, and are arranged in a manner such that the hinges M areequidistantly spaced from one another with respect to a center positionlying in a plane which extends to include therein an axis of the driveshaft 34 and pass through a predetermined position of the swash plate 37at which the swash plate 37 is engaged with one of a plurality ofpistons 38 brought to a top dead center "T" thereof. More specifically,the hinge means having the pair of hinges M is arranged between the twosupport arms 35a of the rotary support 35 and front ends of the pair ofswing plates 37a.

Both support arms 35a of the rotary support 35 are axially rearwardlyextended, and arranged to be symmetrical with respect to theabove-mentioned plane including therein the axis of the drive shaft 34and passing through the predetermined position of the swash plate 37 atwhich the swash plate 15 is engaged with the piston 38 brought to thetop dead center "T" thereof. The support arms 35a have an elongatedthrough-bore 35b. respectively, in which an end of each of a pair ofhinge pins 37b is engaged. The other end of each of the hinge pins 37bis fixed to the associated one of the pair of swing arms 37a of theswash plate 37. The hinge pins 37b of the hinges "M" of the presentembodiment are arranged to be coaxial with each other in a directionvertical to the axis of the drive shaft 34 as clearly illustrated inFIG. 6. Thus, fulcrum positions P₁ and P₂ of the pair of hinges M arearranged to be symmetrical with respect to a plane extending to includetherein an axis of the drive shaft 34 and passing through apredetermined position of the swash plate 37 at which the swash plate 37is engaged with one of a plurality of pistons 38 brought to the top deadcenter "T" thereof. Namely, the fulcrum positions P₁ and P₂ of the pairof hinges "M" can act in the same manner as those of the pair of hinges"K" of the first embodiment of FIGS. 1 and 2. Namely, as shown in FIG.3, in accordance with the above-described symmetrical arrangement of thehinge positions P₁ and P₂ of the pair of hinges M of the hinge means,the hinge position P₁ provides a pivotal connection between one of thesupport arms 35a of the rotary support 35 and one of the swing arms 37aof the swash plate 37, acting to move each single headed piston 38 to anintermediate position of the entire compression stroke thereof, and thehinge position P₂ provides a pivotal connection between the other of thesupport arms 35a of the rotary support 35 and the other of the swingarms 37a of the swash plate 37, acting to move each piston 19 to anintermediate position of the entire suction stroke thereof.

The swash plate 37 has flat faces on opposite sides thereof, and ismounted around the drive shaft 34 via a sleeve element 36 slidablymounted on the drive shaft 34. The sleeve element 36 has formed thereina spherical outer face in spherical contact with a central hub portionof the swash plate 37. Therefore, the swash plate 37 can be rotatedtogether with the drive shaft 34 and turned about the sleeve element 36to change an angle of inclination thereof with respect to a planeperpendicular to the axis of the drive shaft 34.

The swash plate 37 is operatively engaged with the plurality of singleheaded pistons 38 reciprocatorily fitted in the cylinder bores 31a ofthe cylinder block 31 via respective pair of shoes 39. Each shoe 39 hasa flat face in contact with one of the flat faces of the swash plate 37,and a spherical face in turnable contact with a spherical recessprovided in a radial cutout of each piston 38. The radial cutout of eachpiston 38 is arranged in an end of the piston opposite to a compressingend face of the piston 38.

The compressor of FIG. 4 is provided with a control valve 41 arranged inthe cylinder block 31 for controlling fluid communication between thecrank chamber 32a and the suction chamber 33a to thereby adjust fluidpressure level in the crank chamber 32a.

When the drive shaft 34 is rotated, the swash plate 37 of the swashplate assembly having an angle of inclination is rotated togethertherewith, and thus the rotation of the inclined swash plate 37 isconverted into a reciprocation of the pistons 38 in the cylinder bores31a via the motion conversion means having the above-mentioned pair ofspherical shoes 39. Therefore, a refrigerant gas is pumped from thesuction chamber 33a of the rear housing 33 into the respective cylinderbores 31a in which the refrigerant gas is compressed by thereciprocating pistons 38. The compressed refrigerant gas is dischargedfrom the cylinder bores 31a toward the discharge chamber 33b of the rearhousing 33. The capacity of the compressed refrigerant gas dischargedtoward the discharge chamber 33b is controlled by adjusting the fluidpressure level within the crank chamber 32a by the control valve

During the above-mentioned compressing operation of the compressor, oneof the hinges M of the hinge means having the hinge position P₁contributes to the absorbing of the entire reaction forces acting fromthe respective pistons 38 in the compression stroke thereof on the swashplate 37 via the motion conversion means in response to the compressionof the refrigerant gas by these pistons 38 in the compression strokethereof, and the other hinge M of the hinge means having the hingeposition P₂ contributes to the absorbing of the entire reaction forcesacting from the respective pistons 38 in the suction stroke thereof onthe swash plate 37 via the motion conversion means in response to thesuction of the refrigerant gas by these pistons 38 in the suction strokethereof. Further, since the two hinges M of the hinge means cancooperate to provide a constant contribution to the absorbing of thereaction forces of the compression and suction of the refrigerant gasduring a complete rotation of the swash plate assembly, the swash plate37 of the swash plate assembly is not subjected to an unfavorablebending moment, and thus the sleeve element 36 on which the assembly isturnably mounted does not suffer from an application of a local load bythe swash plate assembly. Namely, the sleeve element 36 is able topermit a smooth turn of the swash plate 37 constantly maintained in aspherical contact with the outer spherical face of the sleeve element36. Thus, a local abrasion of the sleeve element 36 does not occur, andaccordingly, noise is not generated during the compressing operation ofthe compressor. Also, a long operation life of the sleeve element 36 andthe swash plate 37 is obtained.

Although the foregoing description is provided in connection with thetwo preferred embodiments of the present invention, many variations andmodifications will occur to persons skilled in the art without departingfrom the scope of the present invention. For example, the pair offulcrum positions P₁ and P₂ of the hinges "K" or "M" may be arranged tobe assymmetrical with respect to a plane extending to include the axisof the drive shaft and passing through a predetermined position of theswash plate 15 or 37 at which the swash plate is engaged with one of thesingle headed pistons 19 or 38 brought to a top dead center thereof asrequired.

Further, the described double fulcrum hinge means is incorporated in avariable capacity swash plate type refrigerant compressor having a swashplate rotated together with the drive shaft, but the double fulcrumhinge means may also be incorporated in a variable capacity swash platetype refrigerant compressor having a swash plate assembly including anon-rotatable wobble plate for driving the reciprocation of the singleheaded pistons.

From the foregoing description it will be understood that, according tothe present invention, since a double fulcrum hinge means for providinga pivotal support between a rotary support of a drive shaft and avariable inclination swash plate assembly has a pair of fulcrumpositions, the hinge means is able to absorb the reaction forces of thecompression and suction of a refrigerant gas without applying a localload to a sleeve element on which the swash plate assembly is turnablymounted. Therefore, the sleeve element does not suffer from a localabrasion, and can smoothly and turnably support the swash plateincreasing the operational life of the compressor.

I claim:
 1. A variable capacity single headed piston swash plate typecompressor comprising:an axially extended cylinder block having frontand rear ends thereof and a plurality of axial cylinder bores formedtherein; a front housing sealingly connected to the front end of saidcylinder block and defining a closed crank chamber therein extending infront of ends of the cylinder bores; a rear housing connected to therear end of said cylinder block and defining therein a suction chamberfor a refrigerant gas before compression and a discharge chamber for therefrigerant gas after compression; a drive shaft rotatably held by saidcylinder block and said front housing with a longitudinal axis thereofextending through said crank chamber; a rotary support element mountedon said drive shaft to be rotated therewith in said crank chamber; avariable inclination rotary swash plate assembly pivotally held by ahinge means and slidably mounted on said drive shaft via a slidablesleeve element for rotation about an axis perpendicular to the axis ofsaid drive shaft to thereby vary an angle of inclination thereof; aplurality of reciprocatory single headed pistons fitted in said cylinderbores of said cylinder block and engaged with said swash plate assemblyvia a motion conversion means for converting rotation of said swashplate assembly into reciprocation of said single headed pistons in saidcylinder bores; and a control valve means for adjusting a fluid pressurein said crank chamber to thereby control the capacity of saidcompressor, said hinge means being provided with a pair of hingesseparately coupled to said swash plate assembly to provide two fulcrumpositions about which said swash plate assembly is pivotally hinged,said two fulcrum positions being spaced apart from one another withrespect to a center position which lies in a plane including the axis ofsaid drive shaft and passing through a predetermined position of saidswash plate assembly at which said swash plate assembly is engaged withone of said plurality of pistons brought to a top dead center thereof.2. A variable capacity single headed piston swash plate type compressoraccording to claim 1, wherein said two fulcrum positions of said pair ofhinges of said hinge means are symmetrically arranged on opposite sidesof said plane, one of said two fulcrum positions absorbing a reactionforce of the compression of said refrigerant gas acting from saidpistons on said swash plate assembly while the other of said two fulcrumpositions absorbs a reaction force of the suction of said refrigerantgas acting from said pistons on said swash plate assembly,
 3. A variablecapacity single headed piston swash plate type compressor according toclaim 1, wherein said pair of hinges of said hinge means comprises:apair of support arms extended toward said swash plate assembly from saidrotary support element; a pair of guide pins arranged in parallel witheach other, and slidably pivoted on said pair of support arms, said pairof guide pins being arranged to be symmetrical with respect to saidplane.
 4. A variable capacity single headed piston swash plate typecompressor according to claim 3, wherein said pair of guide pins of saidpair of hinges of said hinge means are pivotally supported on said pairof support arms via turnable ball elements received in spherical raceelements, said pair of guide pins passing through said turnable ballelements.
 5. A variable capacity single headed piston swash plate typecompressor according to claim 1, wherein said pair of hinges of saidhinge means comprises:a pair of support arms extended toward said swashplate assembly from said rotary support element; a pair of guide pinsarranged to be coaxial with each other, and slidably fitted in said pairof support arms, said pair of guide pins being arranged to besymmetrical with respect to said plane.
 6. A variable capacity singleheaded piston swash plate type compressor according to claim 5, whereinsaid pair of guide pins of said pair of hinges of said hinge means arepivotally and slidably fitted in a pair of elongated through-boresformed in said pair of support arms.
 7. A variable capacity singleheaded piston swash plate type compressor according to claim 1, whereinsaid slidable sleeve element has a spherical outer face thereof on whichsaid swash plate assembly is turnably and slidably mounted.